The Kingdom of Morocco in North Africa is reputed to be the third oldest nation in Africa, after Egypt and Ethiopia. The most westerly state in the Arab world, Morocco is bounded by the Mediterranean Sea, Algeria, the Western Sahara, and the Atlantic Ocean. The history of the region comprising present-day Morocco has been shaped by the interaction of the original Berber population with several ancient civilizations (Phoenician, Carthaginian, Hellenic, Roman) and other more recent cultures (Arab, Portuguese, French, Spanish). Historically, there has been a noteworthy degree of political and economic stability and continuity in the country, along with a diverse population including Christians and Jews, as well as the Sunni Muslim majority. The long survival of the established monarchy and its position as a religious as well as secular institution provided the government with deep-rooted legitimacy. About three-quarters of all present-day Moroccans are of Berber descent, while Arabs, who first arrived in the 7th century, form the second largest ethnic group. Moroccans thus base their identity on their common lineage as a people and the structure and nature of the power relationships that exist in their society. They have the earliest treaty relationship with the United States, dating to the 1787 Treaty of Peace and Friendship.